The inventive concepts described herein relate to a semiconductor memory device, and more particularly, relate to a nonvolatile memory device and/or a memory controller to control the nonvolatile memory device.
Semiconductor memories are usually considered to be the most vital microelectronic component of digital logic system design, such as computers and microprocessor-based applications ranging from satellites to consumer electronics. Therefore, advances in the fabrication of semiconductor memories including process enhancements and technology developments through scaling for higher densities and faster speeds help establish performance standards for other digital logic families.
Semiconductor memory devices may be characterized as volatile random access memories (RAMs), or non-volatile memory devices. In RAMs, the logic information is stored either by setting the logic state of a bistable flip-flop such as in a static random access memory (SRAM), or through the charging of a capacitor as in a dynamic random access memory (DRAM). In either case, the data are stored and can be read out as long as the power is applied, and the data are lost when the power is turned off; hence, these memories are called volatile memories.
Non-volatile memories, such as Mask Read-Only Memory (MROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), and Electrically Erasable Programmable Read-Only Memory (EEPROM), are capable of storing the data, even with the power is turned off. The non-volatile memory data storage mode may be permanent or reprogrammable, depending upon the fabrication technology used. Non-volatile memories are used for program and microcode storage in a wide variety of applications in the computer, avionics, telecommunications, and consumer electronics industries. A combination of single-chip volatile as well as non-volatile memory storage modes is also available in devices such as non-volatile SRAM (nvSRAM) for use in systems that require fast, programmable non-volatile memory. In addition, dozens of special memory architectures have evolved which contain some additional logic circuitry to optimize their performance for application-specific tasks.
A Charge Trap Flash (CTF) technology is being applied to a nonvolatile memory device. The CTF technology is a semiconductor memory technique used to implement nonvolatile NOR and NAND flash memories. The CTF technology is different from conventional floating gate MOSFET technology in that it uses a silicon nitride film to store electrons rather than the doped polycrystalline silicon typical of a floating gate structure. This approach allows memory manufacturers to reduce manufacturing costs five ways: (1) Fewer process steps are required to form a charge storage node, (2) Smaller process geometries can be used (therefore reducing chip size and cost), (3) Multiple bits can be stored on a single flash memory cell, (4) Improved reliability, and (5) Higher yield since the charge trap is less susceptible to point defects in the tunnel oxide layer.